The overall object of this work is to develop a total hip prosthesis with a much longer lifetime than those presently available. This will be done by selecting materials for the components that will minimize wear. Although the total hip replacement has met with considerable success, failures continue to occur due to inadequate attention to design and materials selection. The basic drawback of presently available total hip prostheses is the limited lifetime which restricts implantation to older patients. An important advance could be claimed if the life of the prostheses could be extended to such a degree that prostheses could be implanted in younger persons under the age of 30 with confidence that they would last most of their remaining active life. Initially, testing will be carried out on specially designed wear machines. Promising materials will be investigated for biological tolerance of the bulk material and wear debris. The successful candidates will be used to fabricate components for total hip prostheses will be tested on a hip joint simulator. Successful conclusion of these tests will allow cllnical trials to commence.